In the installation of sewer systems and the like, it is common practice to use a structure known as a "sewer chimney" to join a lower sewer main line to an upper sewer branch line. A sewer chimney is usually constructed as an appurtenance to a deep sewer to allow the branch line (building connection or lateral) to be installed at a shallower depth. These chimneys vary in height and in pipe size, but are commonly 3 to 12 ft. high with a 6" pipe size, these dimensions being typical for a residence or small commercial building. Historically, sewer chimneys have been constructed in place by various methods, some of which are unsatisfactory from a structural standpoint and others of which are time-consuming and expensive. The procedure for building a chimney according to the best available technology would be about as follows:
After the sewer pipe and its associated T-fitting has been installed, a wooden form is built in the trench around the tee. Steel reinforcing bars are sometimes installed and concrete is poured into the form until it reaches a level above the pipe. This concrete (and steel) provides an arch over the sewer pipe and a base for the balance of the chimney structure. The trench must then be kept open and free of water until the concrete has set properly. This should be the case, but it is seldom carried out, due to the cost involved, because of the delay, etc. Excessive water in the trench can also seriously weaken the concrete. The second step (usually the following day) consists of assembling the chimney from sections of pipe and wye branch fittings to the correct elevation. A second form is then constructed around the chimney pipe and fittings for the entire height and concrete is poured into the form. Additional time is required for this concrete to set before the forms can be stripped and before back-filling of the trench can proceed.
Some of the more serious problems connected with this construction technique are that it is a lengthy and costly procedure when performed correctly. Also, subsequent settling of the sewer and/or chimney often results in structural failures, thus allowing infiltration to occur and necessitating expensive repairs. Furthermore, damage to or "loss" of the structure can occur during back-filling, due to the low strength of the concrete at this stage. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a sewer chimney which is of high quality, which is pre-constructed, and which is formed of reinforced concrete ready for on-site assembly.
Another object of this invention is the provision of a sewer chimney, including a reinforced pre-cast concrete bridge structure, which provides an exceptionally strong arch over the sewer and a very stable base, due to its large bearing area; this entire bridge assembly results in the mainline pipe having no bearing weight whatever from the chimney.
A further object of the present invention is the provision of a sewer chimney structure, including a unique sealing arrangement which eliminates infiltration or exfiltration.
It is another object of the instant invention to provide a sewer chimney, including a diaphragm seal which allows for vertical displacement or settling in either the sewer or the chimney structure, thus eliminating the cause of many chimney failures.
A still further object of the invention is the provision of a sewer chimney in which the top section may be rotated to accommodate almost any combination of angles which may be necessary to make a lateral connection.
It is a further object of the invention to provide a sewer chimney formed of sections which are easily stacked vertically and which bolt together to form a rigid structure.
It is a still further object of the present invention to provide a sewer chimney which is inexpensive to purchase and install, which permits the contractor to begin and finish several sewer chimneys in a single day, which permits back-filling of the hole on the same day, and which includes no form work or use of wet concrete.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.